Custom logo

With 3.0.5.4sp8 I had a custom logo that I replaced the existing header_logo.png with.
Now that I have upgraded to 3.1.9, the login screen is different but have dug a little bit to see that a custom logo must be defined in the sys_ini table of the dbconfig database. However, in looking at the default logo it's in in the format of "data:image/png; base64, <long string of characters>".

So my question is, when we edit the custom_logo, what type of field are we suppose to use in the Text dropdown box and then how do we format the data in the data box so that the header_logo.png file that I originally replaced comes up rather than the default ISPConfig logo??